A new class of overrunning roller clutch was defined with the issuance of U.S. Pat. No. 4,821,856 to Lederman, assigned to the assignee of the subject invention. An entirely new component, called a control car, is fitted around each cylindrical roller, and slides back and forth with the roller between the cage side rails as the clutch operates. The control car provides numerous advantages, including highly secure, pre-installation shipping retention for both the rollers and springs. After installation, the cars can provide spin and skew control to the rollers, as well as better retention of the springs. As each control car moves back and forth with its roller, it receives guidance and control from the cage, and in some cases from the pathway race, but does not interfere with the free circumferential motion that allows the roller to continually maintain its lockup ready position.
The degree to which the control car is guided by the cage varies with the particular cage and car design used. In one embodiment disclosed in the above patent, side flanges on the car diagonally overlap with side rails on the cage, but are not completely confined by the cage. That is, each car side flange is prevented from moving in one radial direction by a side rail, but not in both directions. While this provides a good measure of cage to car guidance after installation, a releasable latch is used to retain the cars to the cage prior to installation. In a second embodiment in the same patent, each car has a pair of rails that are totally confined within, and closely guided by, matching tracks in the journal blocks. However, a pair of end rings must be used to retain the journal blocks and cars together, which are not needed in the first embodiment.
Despite the numerous potential advantages provided by the control cars, a drawback of the designs described above is that each control car and journal block must be handled as a separate piece when the roller clutch is assembled. Many roller clutches contain eight to sixteen rollers, meaning that eight to sixteen individual control cars must be separately handled, as well. Later patents have disclosed new designs intended to ease the task of assembling the separate control cars. For example, U.S. Pat. No. 4,924,980 to Lederman discloses a control car that may be inserted freely between the side rails of the cage with straight line, orthogonal motions only, with no need for tipping or forcing the car between the rails. U.S. Pat. No. 4,924,981 to Lederman discloses a control car in which specially designed flanges freely enter clearance slots on the cage side rails as the car is installed, but are blocked from re entering the slots once the spring has been added. Neither design deals with the fundamental problem that each car has to be handled and assembled as a separate piece, however.